the s s united states, this enormous ship that is now writing in philadelphia. i hope it can be saved. >> host: do you have any advice for authors writing history? >> guest: thank you for everyone calling the doctor which is an honorary degree the thank you all the same. >> guest: advice on writing history. >> guest: on how one should start writing history. >> host: i will let you take it any way you want. >> guest: i think two pieces of advice. if you are writing history realize you can't do it three minutes after the event concerned. it is not history. the other thing is the kind of history i practice don't put your private agenda or emotional agenda into your work and if you must, make sure they are clearly labeled. sometimes that doesn't happen. >> host: kerri feinberg's e-mail from illinois, it seems -- [talking over each other] >> host: we rarely get a chance to truly know presidential challenger so basically take all things on chance with one glaring exception, herbert hoover. what lessons do we take from the enormous change of national tide from adoratio